[Nouveau] [PATCH] mm: remove extra ZONE_DEVICE struct page refcount

[Christoph Hellwig]

On Mon, Sep 14, 2020 at 04:10:38PM -0700, Dan Williams wrote:
> You also need to fix up ext4_break_layouts() and
> xfs_break_dax_layouts() to expect ->_refcount is 0 instead of 1. This
> also needs some fstests exposure.

While we're at it, can we add a wait_fsdax_unref helper macro that hides
the _refcount access from the file systems?